Buffers are often called voltage followers because they have substantially unity voltage gain. They are basically current amplifiers that have a low output impedance and a high input inpedance. Their output voltage swing approaches the operating supply voltage and they typically have large slew rates and wide bandwidths. The basic transistor emitter follower is a classical buffer.
From an applications standpoint buffers serve as signal isolation devices, line drivers and signal sources. They are often used in combination with an operational amplifier (op amp) where the buffer is used to isolate the op amp from its load.
The LH0002 is an industry standard buffer, the characteristics of which will be described in some detail hereinafter. Other standard buffers are the LH0033 and LH0063 family which is known for its very high input resistance and for its high speed and very high slew rate. All of these devices employ hybrid construction in their manufacture.